An example of a wireless metropolitan area network (WMAN) 100 is illustrated in FIG. 1. The WMAN 100 includes one or more base stations (BS) 110 each communicating over a radio link (R1) with one or more mobile stations (MS) 120. Each BS 110 can also communicate with an access service network gateway (ASN-GW) 130 (or simply, ASN) over another communication (R6) link. The ASN 130 may further communicate with a connectivity service network (CSN) over an R3 link (not illustrated).
The BS 110 and the MS 120 can communicate with each other according to an existing radio protocol architecture such as the WiMax OFDMA WMAN IEEE 802.16e as illustrated in FIG. 2. The existing IEEE 802.16e standard defines two major layers—the physical (PHY) and the medium access control (MAC) layers. The PHY layer generally corresponds to layer 1 (L1) and the MAC layer generally corresponds to layer 2 (L2) and may include some layer 3 (L3) functionalities.
The MAC layer itself is further split into sublayers including the service-specific convergence sublayer (CS), the MAC common part sublayer (CPS), and the security sublayer. As the name suggests, the CS sublayer provides service specific convergence functions. These generally include mapping external network data, such as ATM or packet (e.g., IP) data, into MAC service data units (SDU) which are sent to the MAC CPS sublayer.
The MAC CPS sublayer performs MAC functionalities such as packing/unpacking the MAC SDUs to MAC protocol data units (PDU) and scheduling the MAC PDUs for delivery to the MS 120 via the PHY layer. Additionally, the CPS sublayer includes the management/control functionalities such as system information broadcast and MS state.
The MAC security sublayer provides MAC PDU encryption services and privacy key management between the BS 110 and the MS 120 to enforce conditional access to the network services.
The PHY layer provides typical physical layer functions including coding, modulation, and MIMO processing.
FIG. 2 shows the two major operational planes of the architecture, one being the data (or user) plane and the other being the management/control plane. The management/control plane includes two types of functionalities: radio resource control (RRC) functionalities and management functionalities. The management/control plane holds a management information base (MIB) that contains radio control information as well as network management information. The CS, CPS, and the security sublayers of the MAC layer interface with the management/control plane components of the architecture and the MIB. The PHY layer also interfaces with the management/control plane components of the architecture.
The existing radio protocol architectures illustrated in FIG. 2 has flaws. For example, the existing protocol layer is a mixture of L3 and higher layer functionalities in L2. Also, the management/control plane interfaces with each of the MAC sublayers as well as with the PHY layer. In short, the structure of the existing radio protocol architecture is not logical.
While such issues may not bring significant problems with isolated deployments, these limitations could pose significant hindrances to system migration and can increase operational expenditures. The mix of protocol layer functionalities introduces interoperability problems as well as problems to migration and evolution of protocol stack. The mixture of protocol layer functionalities also restricts the options for various deployments scenarios ASN profile A, B, C deployment as per the following document: WiMax Forum Network Architecture—Stage 3—Detailed Protocols and Procedures—Release 1.1.0. Additionally this may add to downgrading of system performance especially for inter-RAT (radio access technology) system mobility.